Now they want me to calculate the activitycoeficients gamma, wich is no problem because you have: Antoines formula to find P and with this pressure I can suimple use : Gamma (activitycoefficient)= 760mmHh / P (:the one you calculate with antoine)

Now the second question is a bit harder: you need to calculate the van laar constants, but how can you do this if you do not now what the mixture is ? (you do not now what X1 or X2 is ?) and you do need them to use van laars equation? or not?

van laar being: ln(gamma) = A / (1 + A/B.x1/x2)² ==> how can I find A and B (van laar constants if I do not know X1 nor X2 ?)